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Water nutrient concentrations in channels in relation to occurrence of aquatic plants: A case study in eastern Croatia

Journal

Hydrobiologia

Volume | Issue number

603 | 1

Pages (from-to)

253-266

Document type

Article

Faculty

Faculty of Science (FNWI)

Institute

Institute for Biodiversity and Ecosystem Dynamics (IBED)

Abstract

In this paper we analyzed nutrient concentration in the channels of eastern Croatia and investigated whether certain plant
species and associations can be used as direct estimators of water quality. One hundred and twenty-two channel sites were
visited and water samples taken for laboratory analysis (pH and concentrations of sulfate, chloride, ammonium, nitrate, and
total phosphorus). At each site, macrophyte vegetation was recognized and its occurrence recorded. Three groups of analyses
were performed: (a) principal component analysis to describe habitat characteristics of the investigated channels, (b) stepwise
regression analysis to build estimation models for nutrient concentrations, and (c) geostatistical analysis including fitting
of variograms and interpolation of values over the whole area of interest. High values of water nutrients in the eastern Croatian
channels were reported (90% intervals): 5.3-29.4 for nitrates, 27.8-54.2 for sulfates, 0.1-0.4 for total P, and 0.18-0.34
mg l(-1) for ammonium. Water nutrient concentrations can be successfully mapped over the channel network in eastern Croatia
using geostatistics (regression kriging). The nutrient concentration variables required log transformation prior to regression
or variogram analysis because their distributions were distinctly skewed towards lower values. Species were found to be a
more successful estimator of nutrient concentrations than plant associations. In all cases, species had a higher adjusted
R-square value, ranging from 0.302 (ammonium) to 0.485 (sulfates). Additional load of nutrients in water could lead to the
disappearance of the more-sensitive species Lemna trisulca, Riccia fluitans, and Ricciocarpus natans and the spread of Potamogeton
pectinatus, Glyceria maxima, and Glyceria fluitans. Further studies are needed to develop strategies for incorporating permanent
monitoring networks to observe environmental changes and succession of vegetation.

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